[mythtv] Re: [patch] DVB auto-pid, take 2

Ed Wildgoose lists at wildgooses.com
Mon Feb 9 14:49:39 EST 2004


Base Commander wrote:

> Thanks for the feedback, Kenneth.
>
> Agreed- I can see why this could cause issues.  I'm very much in 
> favour of eliminating the dvb_pids table, since most DVB receivers 
> would normally use the PMT to determine the correct PIDs.  We can use 
> the cached PMT from the channel table (if available) to read out the 
> last transmitted PID and just re-use it.
>
> The reason that I'm hoping to get this in is that I've got a full 
> NIT-scanning implementation that we can use to auto-determine the 
> available channels, given an initial transponder's tuning 
> information.  It's a lot cleaner to do the PID detection at channel 
> switch time, rather than channel scan time, especially since some 
> channels may come on/offline during the day.
>
> To address the multiple-audio-PID issue - should we have a dvb_lang 
> table with language priority for each channel source?  We could just 
> use the following logic:
>
> 1.  If one or more of the audio PIDs in the PMT match the dvb_lang 
> table, use the one with the highest priority.
> 2.  If there are more than one audio PID in the PMT with the same 
> language, and this language is the highest priority, take the first 
> one (in PMT order).
> 3.  If there are no audio PIDs with languages in the dvb_lang table 
> (or none of the PIDs have language identifiers), take the first one 
> (in PMT order).
>
> This should handle all of the channels that I can see here.  Most of 
> them have either no MPEG language tag, or "eng" as the specified ISO 
> language.
>

I think that some channels have an option of AC3 or stereo.  It would be 
extremely handy to have the option to auto pick the AC3 when its 
available and fall back to stereo otherwise (not everyone will want AC3, 
and AC3 will not be available for all programs)

Any suggestions on how this would work?

Ed W


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